In recent years, the wireless communication technique has been greatly developed. However, a problem concerning how to improve time-varying channel estimation performance as far as possible in the case of a time-varying channel exists in the wireless communication technique all the time. Besides, this problem is becoming more and more prominent and serious along with the continuous expansion of the fields to which the wireless communication technique is applied.
For example, in a traditional mobile communication system, such as a 2G or 3G mobile communication system, the design of the system always focuses on the cases of medium and low motion speeds. However, a demand for realizing high-speed transmission of data at a high motion speed arises along with the popularity of bullet trains and high-speed rails. The traditional mobile communication system designed directed to the cases of medium and low motion speeds fails to satisfy such a demand, because a high-speed motion environment will cause a fast time-varying characteristic of a wireless communication channel. If a receiver performs coherent demodulation, the fast time-varying characteristic of the channel will make channel estimation and tracking extremely difficult.
The traditional channel estimation method is always based on a condition that multipath time-varying channel parameters are known, without considering the complexity of channel estimation. However, the multipath time-varying channel parameters are unknown due to the fast time-varying characteristic of the wireless communication channel. Besides, in a case where the multipath time-varying channel parameters are known, the complexities of demodulation and detection algorithms are still relatively high.
In addition, the traditional method fails to essentially solve the problem of inter-subcarrier interference (ICI) caused by the fast time-varying characteristic of the channel. In the current mobile communication systems for business, a pilot-based channel estimation manner has been widely used. In a time-varying channel environment, positions of pilot symbols suffer from serious ICI, such that the channel estimation performance is abruptly worsened. It is difficult for the pilot symbol mapping scheme designed directed to the cases of medium and low motion speeds to satisfy the performance requirements of the system in the high-speed motion environment. On one hand, in the traditional pilot symbol mapping scheme, pilots are transmitted non-continuously in time and frequency domains, which is based on an assumption that the wireless communication channel does not vary within one demodulation symbol period. However, this assumption is approximately tenable in the cases of medium and low motion speeds, but in a high-speed motion environment, the wireless communication channel varies within one demodulation symbol period. On the other hand, in the high-speed motion environment, it is necessary to transmit pilot symbols within each demodulation symbol period, and at this time pilot overheads of the system rapidly increases, thus greatly influencing the throughput and the frequency utilization rate of the system.
Thus, it is desired to, with respect to the high-speed motion environment, optimize the design of the pilot symbol mapping scheme to improve the phenomenon of ICI, adapting to the fast time-varying characteristic of the wireless communication channel, and making it possible to effectively control the overheads of the pilots, thus improving the channel estimation performance.
With respect to the above problem existing in the prior art, a transmitting apparatus and a receiving apparatus as well as a corresponding transmitting method and a corresponding receiving method according to the present invention are proposed.